Hmm, you weren't quite specific on how you tried to access the forums. Did you use a wap browser on your mobile, or a full blown mobile browser over GPRS? If it is the former(guessing from the subject), then it will not work for you. There must be specially designed web pages for wap, and I doubt the forum software supports this. Wap pages are written in WML (wireless markup language) which is a stripped down version of HTML. In other words: to view a site using wap, special pages must exist written in WML and not HTML. I hope some things are clearer for you now

are you using the phone's builtin browser? This browser (just checked from siemens site) supports WAP only, so normal html pages cannot be displayed. My guess is that since wml and html in their basics are similar (some tags are the same), some can be interpreted correctly from your phone, but some of them are not, hence the error message.